wireprotov2: change how revisions are specified to changesetdata Right now, we have a handful of arguments for specifying the revisions whose data should be returned. Defining how all these arguments interact when various combinations are present is difficult. This commit establishes a new, generic mechanism for specifying revisions. Instead of a hodgepodge of arguments defining things, we have a list of dicts that specify revision selectors. The final set of revisions is a union of all these selectors. We implement support for specifying revisions based on: * An explicit list of changeset revisions * An explicit list of changeset revisions plus ancestry depth * A DAG range between changeset roots and heads If you squint hard enough, this problem has already been solved by revsets. But I'm reluctant to expose revsets to the wire protocol because that would require servers to implement a revset parser. Plus there are security and performance implications: the set of revision selectors needs to be narrowly and specifically tailored for what is appropriate to be executing on a server. Perhaps there would be a way for us to express the "parse tree" of a revset query, for example. I'm not sure. We can explore this space another time. For now, the new mechanism should bring sufficient flexibility while remaining relatively simple. The selector "types" are prefixed with "changeset" because I plan to add manifest and file-flavored selectors as well. This will enable us to e.g. select file revisions based on a range of changeset revisions. Differential Revision: https://phab.mercurial-scm.org/D4979

https://bz.mercurial-scm.org/1877

  $ hg init a
  $ cd a
  $ echo a > a
  $ hg add a
  $ hg ci -m 'a'
  $ echo b > a
  $ hg ci -m'b'
  $ hg up 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg book main
  $ hg book
   * main                      0:cb9a9f314b8b
  $ echo c > c
  $ hg add c
  $ hg ci -m'c'
  created new head
  $ hg book
   * main                      2:d36c0562f908
  $ hg heads
  changeset:   2:d36c0562f908
  bookmark:    main
  tag:         tip
  parent:      0:cb9a9f314b8b
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     c
  
  changeset:   1:1e6c11564562
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     b
  
  $ hg up 1e6c11564562
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  (leaving bookmark main)
  $ hg merge main
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg book
     main                      2:d36c0562f908
  $ hg ci -m'merge'
  $ hg book
     main                      2:d36c0562f908

  $ cd ..